Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$117.27	9.546%	$128.4646	$128.46	$128.45	$128.50
Purchase #2	$74.63	8.741%	$81.1534	$81.15	$81.15	$81.20
Purchase #3	$167.90	8.323%	$181.8743	$181.87	$181.85	$181.90
Purchase #4	$121.70	13.207%	$137.7729	$137.77	$137.75	$137.80
Purchase #5	$115.45	7.218%	$123.7832	$123.78	$123.80	$123.80
Purchase #6	$175.83	13.328%	$199.2646	$199.26	$199.25	$199.30
Purchase #7	$184.66	13.427%	$209.4543	$209.45	$209.45	$209.50
7 purchase totals =	$957.44		$1,061.7673	$1,061.74	$1,061.70	$1,062.00